If you run it as root with no arguments, it will iterate through /proc/*/maps, pick out rx-p (readable & executable) mappings with a non-zero inode (corresponding to an exe, or an so) and for each address in the range count how many times each physical pages is mapped. Finally, it outputs how many pages were saved through sharing (i.e., w/o sharing that many extra pages of physical memory would have been consumed).

I ran it inside a stock Centos 7 VM with 1GB system memory, and firefox (no tabs), emacs and a terminal running. It outputted a saving of ca 16500 pages, corresponding to about 62MB of saved memory.

It'd be interesting to run it under KDE with a number of widgets and other fancy stuff running, just for comparison.